You just have to set realistic expectations. Some internet people have done tests and concluded that it does extend the life of a wine by a couple of days, and some internet people have not found a difference. Based on anecdotes from a friend, it works better on some wines than others. I haven't searched hard to enough to come across anyone claiming that it makes things worse.

For a $12 thing, it's not a huge investment to get one and see for yourself whether it works or not.